Particle simulations of a Hall thruster plume

A numerical code that combines the direct simulation Monte Carlo method wit h the particle-in-cell method has been developed to examine the plumes of H all thrusters. The present investigation includes a study of the sensitivit y of the computed plume to various ion conditions at the thruster exit and considers models for computing the electric field based on the electron mom entum equation. Specifically, two electrostatic models are compared: one as sumes isothermal electrons, whereas the other uses a variable electron temp erature model. Computations are compared with experimental measurements of current density, ion velocity, ion density, electron density, heat flux, an d plasma potential in the plume of a stationary plasma thruster. The varyin g electron temperature is found to affect the very near field significantly . Simulations using this model agree better with near-field current density measurements. This model also leads to better agreement with electron numb er density measurements in the far field. The agreement of plasma potential depends on parameters used in the simulations. To better represent the flo w inside the experimental facilities, the full chamber geometry is simulate d assuming symmetry about the thruster centerline. These simulations lead t o excellent agreement with current density measurements to 180 deg. The sen sitivity study indicates that the far-field current density is relatively e asy to reproduce.